1. Field of the Invention
The present invention relates to an antenna-integrated module suitable for a small-sized transmitter-receiver used for communication and broadcasting.
2. Description of the Related Art
In recent years, accompanying with the development of wireless communication techniques, various electronic apparatuses or wireless cards in which small-sized transmitter-receiver units are mounted have been proposed. This kind of transmitter-receiver unit is an antenna-integrated high frequency module in which an antenna element is mounted on a circuit board with a high frequency circuit. In the conventional antenna-integrated module, in general, a shield case composed of a metal plate covers a specific region of the circuit board on which the main parts of the high frequency circuit are arranged. An antenna element, such as a chip antenna or a pattern antenna, is provided on the other regions of the circuit board, which is disclosed in Japanese Unexamined Patent Application Publication No. 2002-232221 (see pages 4 to 6 and FIG. 1).
In such a conventional antenna-integrated module, the high frequency circuit comprises a wiring pattern that is formed on the upper surface, etc., of the circuit board, various electronic parts, such as chip parts and ICs that are connected to the wiring pattern, and a ground pattern that is formed on the lower surface or in an inner layer of the circuit board. A part of the wiring pattern extends toward the outside of the shield case to be connected to a feeding portion of the antenna element. In addition, the ground pattern is connected to a ground portion of the antenna element through a via hole provided in the circuit board and is also connected to the shield case. Since the shield case is mounted to the circuit board in a state in which it covers the main parts of the high frequency circuit, the high frequency circuit is maintained in a state in which it is almost shielded from an electromagnetic field.
As described above, in the conventional antenna-integrated module, both the antenna element and the shield case are provided on the circuit board, and the shield case covers the main parts of the high frequency circuit. Therefore, although the shield case and the antenna element are arranged as close to each other as possible, the entire size of the module is a little large in plan view. Thus, it is difficult to decrease the size of the module. In addition, in the conventional antenna-integrated module, since the antenna element must be provided in limited space on the circuit board, the size of the antenna element itself is strictly restricted, and thus it is difficult to achieve an antenna-integrated module having a high gain. Furthermore, in the conventional antenna-integrated module, a space for the antenna element is small. Therefore, in order to obtain the desired electric field in the radiation conductor portion, an additional antenna element, such as a chip antenna, has to be mounted on the circuit board. As a result, the number of parts and manufacturing costs of the module are increased.